Funky ...
I've been commuting for years in a pretty heavily-congested suburb of Philadelphia. There are a few boneheads out there that don't like to share the road with cyclists, but I find them pretty easy to ignore now. I remember them being pretty unsettling early on. There are many, many more drivers that go out of their way to accomodate us, and I am grateful for them.
Clothes ... I pack a duffle bag with several changes of "unmentionalbes", socks, t-shirts, and an extra thing of deodorant. I bring it in when I am forced to drive, and I keep it stowed at work for those "just-in-case" days. I also leave a pair of shoes at work, so I don't need to bring them in every day. Because I leave the house at 4:45 in the morning, I find those just-in-case moments happen more than I would imagine.